Myocardial perfusion imaging (MPI) is a diagnostic technique useful for the detection and characterization of coronary artery disease. Perfusion imaging uses materials such as radioisotopes to identify areas of insufficient blood flow.
Radioisotopes are commonly used in contemporary medical imaging. One of the most important clinically-employed radioisotopes is technetium-99m (99mTc). Other radioisotopes, including halogens, such as 18F, 125I, 131I and 82Br, and isotopes of various metal radionuclides of lead, gallium, rhenium, rubidium, arsenic and copper, have also been explored as potential imaging agents. Medical imaging is used in a variety of medical applications, including imaging of the brain, tumors, and components of the cardiovascular system.
Perfusion agents are currently one of the most important tools for determining heart function. Tl-201, Tc-99-MIBI and Tc-99-tetrofosmin are in routine use for myocardial imaging at rest and after exercise. These agents are very useful but are not optimal. These tracers are single-photon imaging agents and the utility is limited by the properties of existing single-photon emission computed tomography (SPECT) imaging cameras and technology. Positron Emission Tomography (PET), however, has several advantages in comparison to SPECT including higher image resolution and more straightforward attenuation correction. Fluorine-18 is a positron-emitting radionuclide whose physical properties (t1/2=110 min., 97% positron yield) are well suited to PET imaging, and the number of PET cameras and imaging centers are growing rapidly in response to the increased availability of 18F, particularly as [18F]FDG (2-fluorodeoxyglucose).
Fluorine-18 is one of the most useful positron emitting radionuclides currently being used in clinical nuclear medicine diagnosis. For example, 2-[18F] FDG (2-[18F]-fluoro-2-deoxy-D-glucose) is the radiopharmaceutical of choice for the diagnosis of several cancers and brain disorders. This radiopharmaceutical produces superior high-resolution images and quantitative data about regional uptake by tissue. The 10-min half-life of 18F allows production and distribution of 2-[18F] FDG to nuclear medicine facilities that do not have access to a cyclotron. The relatively long physical half-life of 18F also permits PET studies of moderately slow physiological process. Decay of 18F is largely by positron emission (97%), and the emitted positron is of relatively low energy (maximum 0.635 MeV) and thus has a short mean range (2.39 mm in water). Fluorine-18 is readily available from both particle accelerators and nuclear reactors using a wide variety of nuclear reactions, and can be produced at specific activities approaching the theoretical limit of 1.171×109 Ci/mmol.
Myocardial perfusion imaging (MPI) is extremely useful in the diagnosis of cardiac disease. PET (positron-emission tomography) MPI provides functional images of high quality that can be co-registered with [18F]FDG images to delineate regions of infarct and ischemia. Short-lived compounds such as [15O]H2O, [13N]NH3, and 82Rb are well established PET MPI tracers, but PET centers without a cyclotron are limited to using 82Rb, which has significant limitations including high cost and high positron energy.
The present invention is directed to overcoming these and other deficiencies in the art.